There are two widely used applications that help you change the color of your Pearl’s trackball. One is offered free (though a donation is appreciated) called “ColorPearl” and the other, “Color Your Trackball” by Cworx, is available for a small $4.95 fee. Both offer multiple colors for your trackball light and are available for an over the air (OTA) download.
There are other tutorials on the web to direct you on how to manually change the color of your trackball light yourself, but unless you consider yourself an expert at such maneuvers, it’s probably best that you use one of the above-mentioned applications instead.
As you will also find in comparing both software applications, both come pretty well recommended by users who have successfully installed them. Still, be sure to always back your BlackBerry up using your Desktop Manager before adding a new application so that you can restore your device to its most recent state should you ever need to.